Liquid fuel injection pumps



Jan. 6, 1970 Filed June 14, 1968 J. P. s. CURRAN ETAL LIQUID FUELINJECTION PUMPS 2 Sheets-Sheet 1 V J 2 5 IN ENTOR awn awe.

1970 J. P. s. CURRAN ETAL 3,487J&

LIQUID FUEL INJECTION PUMPS Filed June 14, 1968 2 Sheets-Sheet 2 INVETOR 7 21.01.10? kuwcm L) cflaudd United States Patent 3,487,783 LIQUIDFUEL INJECTION PUMPS John Patrick Stewart Curran, Tuifley, and DavidElliot, Stroud, England, assignors to Bryce Berger Limited,Gloucestershire, England Filed June 14, 1968, Ser. No. 737,143 Int. Cl.F0411 13/042, 17/00; F15b 11/08 U.S. Cl. 10350 4 Claims ABSTRACT OF THEDISCLOSURE A fuel injection pump comprising a reciprocable plunger whichduring inward movement displaces fuel until a spill port is opened, apiston being provided to effect inward movement of the plunger and thepiston having fluid pressure applied thereto from a source by way of avalve and a flow regulator, the flow regulator acting to limit the rateof flow of fluid when the port is opened.

This invention relates to liquid fuel injection pumps for supplying fuelto a combustion space of an internal combustion engine and of the kindcomprising in combination, a pump plunger which during a pumping strokedisplaces fuel from a pumping chamber to the engine, the termination ofdischarge to the engine being effected by the uncovering of a spill portby the plunger at a predetermined position during the pumping stroke,and a fluid pressure operable piston contained within a cylinder forimparting movement to the plunger, said cylinder being arranged toreceive fluid under pressure from a source in timed relationship withthe engine.

With such a pump when the spill port is opened, the force which opposesmovement of the plunger and piston is suddenly reduced with the resultthat rapid acceleration of the plunger and piston occurs. The plungerand piston must eventually be arrested, and the object of the presentinvention is to provide in such a pump means whereby the suddenacceleration is minimised.

According to the invention in a pump of the kind specified, a flowregulator is provided to control the flow of fluid into said cylinder,said flow regulator being adjusted so that when the resistance to theflow of fluid decreases, as a result of the spill port being uncoveredby the plunger, the flow regulator moves to restrict the rate of flow offluid into the cylinder, thereby limiting the acceleration of theplunger and piston.

In the accompanying drawings:

FIGURE 1 is a sectional side elevation showing one example of a pump inaccordance with the invention, and

FIGURE 2 is a view of part of the pump shown in FIGURE 1 to an enlargedscale.

Referring to the drawings there is provided a pumping plunger which isaccommodated within a cylindrical bore formed in the body part of thepump. The inner end of the bore is in communication with an outlet 11,and for controlling the flow of fuel through this outlet, there isprovided a non-return delivery valve 12. In use, the outlet is connectedto a fuel injection nozzle 13 which is arranged to direct fuel into acombustion space of an engine with which the pump is associated.

Formed in the wall of the bore is a spill part 14 which is incommunication with a fuel supply chamber 15 formed in the body part andwhich, in use, is connected to a source of liquid fuel. Formed on theperiphery of the plunger is a helical groove 16 which is incommunication with the pumping chamber defined by the bore. In use,during inward movement of the plunger 10, fuel is expelled from thepumping chamber by way of the outlet 11 until the helical groove 16 isexposed to the spill port 14, whereafter the delivery of fuel to theengine ceases, and the remaining fuel in the pumping chamber is expelledthrough the spill port. During outward movement of the plunger, as soonas the port 14 is uncovered, fuel from the supply chamber 15 flows intothe pumping chamber and completely fills same.

The plunger is loaded in the outward direction by means of a coiledcompression spring 17 and for moving the plunger inwardly against theaction of the spring, a fluid pressure operable piston 18 is provided.This is located within a cylinder 19 which may be formed in the bodypart of the pump or in a part adapted to be secured thereto.

There is also provided a source 20 of fluid under pressure and this maycomprise a pump which is driven by the engine and which supplies fluidto an accumulator. Fluid under pressure is supplied to the cylinderunder the control of a valve 21 which is operated in timed relationshipto the engine, and the arrangement is such that when the valve isopened, fluid under pressure acts on the piston 18 to effect inwardmovement of the plunger 10.

The return motion of the piston 18 and the plunger 10 is effected byclosing the valve 21 and opening a valve 25 which is operated insynchronism with the valve 21. The valve 25 when opened allows fluid toflow from the cylinder 19 to a drain.

Such systems are fairly well known, and one of the problems with such asystem is the fact that as soon as the spill port 14 is opened to thehelical groove 16, the force restraining the inward movement of theplunger and piston is reduced, with the result that rapid accelerationoccurs, and the plunger and piston attain a high velocity and eventuallymust be stopped either by positive stops or by means of dash pots.

In the present system a flow regulator 23 is provided to control theflow of fluid into the cylinder. As shown in FIGURE 2 the flow regulatorcomprises an elongated cylindrical chamber 30, the opposite ends ofwhich are closed by adjustable plugs 31, 32. The plug 31 constitutes astop, and the other plug constitutes an abutment for a coiledcompression spring 33. Intersecting the chamber is a flow passage 34through which fluid is arranged to flow to the cylinder containing thepiston, and slidably accommodated within the chamber is a regulatorelement 35 upon one end of which acts the spring. The regulator elementis of reduced section intermediate its ends and at a positioncorresponding to the flow passage. Moreover, the end of the element uponwhich the spring 33 acts is exposed to the pressure at the downstreamend of the flow passage, and the other end of the valve element isexposed to the pressure at the upstream end of the flow passage.

In use, the plugs 31, 32 are adjusted so that the regulator offerslittle restriction to the flow of fluid to the cylinder 19 when thespill port 14 is closed. However, when the spill port is opened and theresistance to the flow of fluid suddenly decreases, the pressure dropwhich occurs between the ends of the flow passage increases sufficientlyto move the regulator element 35 against the action of the spring. Thismovement restricts the effective area of the flo'w passage so that therate at which fluid can pass to the cylinder is also restricted, and theacceleration of the piston and plunger is limited. Furthermore, becauseof the increased restriction to flow, the pressure drop also increases,the final result being complete closure of the flow passage. Adjustmentof the plug 32 enables the regulator to be adjusted to operate at agiven pressure drop, whilst adjustment of the plug 31 serves to enablethe regulator to be adjusted to operate at a given flow.

Having thus described our invention, what We claim as new, and desire tosecure by Letters Patent is:

1. A liquid fuel injection pump for supplying fuel to a combustion spaceof an internal combustion engine and of the kind comprising incombination, a body in which is defined a bore, a pump plunger slidablewithin the bore and which during a pumping stroke displaces fuel fromthe bore to the engine, a spill port which is uncovered by the plungerat a predetermined position during the pumping stroke to terminate thedischarge of fuel to the engine, a fluid pressure operable pistoncontained within a cylinder for imparting movement to the plunger, and aflow regulator for controlling the flow of fluid into said cylinder froma source, said flow regulator being adjusted so that when the resistanceto the flow of fluid decreases, as a result of the spill port beinguncovered by the plunger, the flow regulator moves to restrict the rateof flow of fluid into the cylinder, thereby limiting the acceleration ofthe plunger and piston.

2. A pump as claimed in claim 1 including a first valve operable insynchronism with the engine to admit fluid under pressure from saidsource to the cylinder through said flow regulator and a second valveoperable in synchronism with the engine to permit fluid to escape fromsaid cylinder.

3. A pump as claimed in claim 1 in which said flow regulator comprises aspring loaded regulator element slidable within a chamber defined in abody part, a flow passage defined in said body part and through whichfluid flows from said source to the cylinder, said chamber in- Ktersecting said flow passage and the element defining a restriction tothe flow of fluid through the flow passage, means biasing the elementtowards one end of the chamber, passage means through which said one endand the other end of the chamber are in communication with the upstreamand downstream ends of the flow passage respectively whereby the elementis exposed to the pressure drop across the restriction the arrangementbeing that when said pressure drop increases due to the reducedresistance to the flow of fluid when the spill port opens, the elementwill move to restrict the rate of flow of fluid through the flowpassage.

4. A pump as claimed in claim 3 including a pair of adjustable plugsserving to close the opposite ends of the chamber, the plug at said oneend of the chamber defining a stop for the valve element whereby thedegree of restriction to the flow of fluid through the flow passage canbe adjusted, and the plug at the other end of the chamber defining anabutment for the spring whereby the force exerted by the spring can beadjusted.

References Cited UNITED STATES PATENTS 1,956,612 5/1934 Brun 1031502,033,579 3/1936 Koster 10337 2,662,476 12/1953 French 103-50 2,756,7247/1956 Stewart et al. 91447 2,879,745 3/1959 Brown 91-447 3,168,0102/1965 Thomas 91447 WILLIAM L. FREEH, Primary Examiner US. Cl. X.R.9l447; 103-37

